Packaging container and method of producing the same

ABSTRACT

A packaging container according to the present invention is molded of a thin synthetic resin sheet. The outer peripheral edge of an opening of the packaging container  1, 18  has an outwardly extemded flange  11 . The outer peripheral edge  11   a  of the flange  11  is corrugated in the vertical or horizontal direction. By corrugating the outer peripheral edge  11   a  of the flange  11 , the corrugated outer peripheral edge  11   a  can give a soft touch to user&#39;s hand or finger or a wrapping film contacting the same. As a result, user&#39;s hand or finger can be prevented from being hurt and the wrapping film can be prevented from being broken.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a packaging container and a method ofproducing the same, and especially to an opening peripheral edgeencompassing an opening of a packaging container.

2. Description of Related Art

Among synthetic resin packaging containers, containers having an insidestorage part formed by sheet molding recently have come to need spacesaving property. Therefore, needs have changed from containers molded ofa foamed sheet to containers molded of thin synthetic resin sheet. Asynthetic resin sheet is molded into a container shape and then theperipheral edge of the container shape is cut, whereby a containermolded of thin synthetic resin sheet can be obtained. Generally, such apackaging container has a shape provided with a wide opening. Apackaging container of this shape comprises a bottom plate, a peripheralside wall upwardly extending from the periphery of the bottom plate, andan opening peripheral edge encompassing an opening and outwardlyextended from the upper edge of the peripheral side wall.

Further, a lid to be put on a container is manufactured also by moldinga thin synthetic resin sheet into a lid shape. Some lids are molded intocomplicated shapes in order to have a good design. However, generally, alid has an opening peripheral edge encompassing a lid opening andextended outwardly, obliquely downwardly or downwardly in order toengage with the upper edge of the peripheral side wall and the openingperipheral edge of the container.

A container or a lid molded of a thin synthetic resin sheet is separatedfrom the sheet by cutting the above-mentioned opening peripheral edgethereof. Therefore, the opening peripheral edge is elongated in straightand/or smoothly curved fashion along the outline of the container or thelid.

As a result, there is a problem that such an opening peripheral edgeelongated along the outline of a container or a lid is apt to hurtuser's hand or finger at the time of using the container or the lidsince the material sheet thereof is thin.

Further, at the time of putting an article into such a container andwrapping the same with a wrapping film, the wrapping film is rubbedagainst the opening peripheral edge and sometimes cut. Therefore, thereis a problem that much time and labor is required to wrap such apackaging container with a wrapping film.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to solve theabove-mentioned problems by providing a method for manufacturing a safeand easily treatable packaging container having an opening peripheraledge of an improved structure.

A packaging container according to the present invention is one whoseopening peripheral edge encompassing an opening is cut, and thecontainer is characterized in that the opening peripheral edge thereofis not elongated straight but is finely corrugated in the longitudinaldirection.

Even though a packaging container according to the present invention ismolded of a thin synthetic resin sheet, the finely corrugated openingperipheral edge in the longitudinal direction thereof has a lowersharpness than a thin peripheral edge elongated straight has. As aresult, if user's hand, finger or the like is rubbed against the openingperipheral edge, the hand, finger or the like can be prevented frombeing hurt.

Further, even if a wrapping film is stretched on and rubbed against theopening peripheral edge, the wrapping film can be prevented from beingbroken.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a container body of a packagingcontainer according to one embodiment of the present invention.

FIGS. 2(A)-2(C) are partly enlarged views of section A of the containerbody of the packaging container of FIG. 1.

FIG. 3(A)-3(C) are partly enlarged views of a main part of a packagingcontainer according to another embodiment of the present invention.

FIGS. 4(A) and 4(B) are enlarged views of a main part of a packagingcontainer according to a further embodiment of the present invention.

FIG. 5 is an illustrative plan view of a container body or a lid of apackaging container for explaining a peripheral edge thereof to becorrugated.

FIG. 6 is an illustrative plan view of a packaging container in which acontainer body and a lid are connected to each other for explaining thepositions of a peripheral edge thereof to be corrugated.

FIG. 7 is a view illustrating an example of the shape of a containerbody of a packaging container and showing the positions to becorrugated.

FIG. 8 is a view illustrating an example of the shape of a lid of apackaging container and showing the positions to be corrugated.

FIG. 9 is a perspective view of an example of a metal mold for molding asheet.

FIG. 10 is a front view showing the cutting operation of a packagingcontainer by a Thomson blade.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 is a perspective view of a container body of a packagingcontainer according to one embodiment of the present invention. AndFIGS. 2(A)-2(C) are a partly enlarged perspective view, a plan view anda front view of section A of the container body 1 of the packagingcontainer of FIG. 1.

In this embodiment, the container body 1 is explained as a packagingcontainer. The container body 1 has a bottom plate 20 and a peripheralside frame (peripheral side wall) 10 standing obliquely outwardly at theperiphery of the bottom plate 20. The bottom plate 20 has, for example,a substantially rectangular shape with rounded four corners. Therefore,the container body 1 has, as a whole, a shape of a deep rectangulardish. And the upper end of the peripheral side frame 10 defines anopening of the container body 1. An outwardly extended flange 11 isformed at the upper end of the peripheral side frame 10. The flange 11constitutes a peripheral flange encompassing the upper end of theperipheral side frame 10, namely, encompassing a container opening. Theflange 11 serves for reinforcing the container opening both in theinward and outward directions.

The outer peripheral edge 11 a of the flange 11 is finely corrugated. Inthe embodiment shown, the outer peripheral edge 11 a of the flange 11 isfinely corrugated when seen in the horizontal direction. In this case,the difference d between the top and the bottom of the corrugated shape(waveform) is not more than 0.5 mm. Further, the pitch p (the distancebetween the tops or bottoms) of the corrugated shape (waveform) is about1 mm.

In this respect, the difference d between the top and the bottom of thewaveform may be in the range of 0.2-1.0 mm and is preferably not morethan 0.5. And the pitch p may be in the range of 0.5-5.0 mm and ispreferably about 1.0 mm.

By determining the size of the waveform in the above-mentioned valueranges, user's hand and finger can be prevented from being hurt and thewrapping film can be prevented from being broken by the outer peripheraledge 11 a of the flange 11.

FIGS. 3 (A)-(C) are a partly perspective view, a plan view and a frontview showing another shape of a flange 11 extended outwardly from theupper end of the peripheral side frame 10 of the container body 1. Inthe embodiment shown in FIGS. 3 (A)-(C), the whole of the flange 11encompassing the container opening is finely corrugated in the verticaldirection. As a result, the outer peripheral edge 11 a of the flange 11is substantially straight in a plan view, but the outer peripheral edge11 a extending in the lateral (horizontal) direction is finelycorrugated in the vertical direction in a side view (seen in thehorizontal direction). The difference d between the top and the bottomof the corrugated shape (waveform) is in the range of 0.2-1.0 mmsimilarly to the above-mentioned embodiment, and the pitch p (thedistance between the tops or bottoms) of the waveform is in the range of0.5-5.0 mm.

The direction of the corrugation of the outer peripheral edge 11 a ofthe flange 11 may be a horizontal direction in which case the waveformscan be seen in plan view as in the above-mentioned embodiment, or may bea vertical direction in which case the waveforms can be seen in thelateral (horizontal) direction as in this embodiment.

Otherwise, by combining the above-mentioned embodiment and thisembodiment, the outer peripheral edge 11 a of the flange 11 may becomplexly corrugated both in the lateral (horizontal) and verticaldirections.

Anyway, since the outer peripheral edge 11 a of the flange 11 is finelycorrugated, the outer peripheral edge 11 a does not form a straight edgesuch as one cut from a flat thin resin sheet but forms a finely waved orcorrugated edge. As a result, the outer peripheral edge 11 a of theflange 11 according to the present invention can prevent user's hand andfinger from being hurt and prevent a packaging film from being broken bycontacting the outer peripheral edge.

FIGS. 4(A) and 4(B) are partly enlarged views illustrating the structureof a flange 11 and an outer peripheral edge 11 a thereof according to afurther embodiment of the present invention.

As shown in FIG. 4(A), minute projections and recesses are formedthroughout the flange 11. That is, a number of minute projections 12protruding on the upper surface side of the flange 11 and a number ofminute recesses 13 depressed on the reverse side of the flange 11 areregularly formed. And as shown in FIG. 4(B), the outer peripheral edge11 a obtained by cutting such a flange 11 forms a vertically corrugatededge defined by a cutting line crossing the number of minute projections12 and a number of minute recesses 13 formed throughout the flange 11.

In the case of this embodiment, the outer peripheral edge 11 a of theflange 11 is also not straight but corrugated, so that the sharpnesswith respect to user's hand and finger and a packaging film can bereduced.

In the above-mentioned embodiments, described are package containershaving a corrugated opening peripheral edge encompassing the opening ofthe container body 1. However, the present invention can be applied notonly to the container body 1 but also to an opening peripheral edge of alid to be put on the container body 1. That is, when a packagingcontainer, especially one for packaging food or the like is molded of athin synthetic resin sheet, not only a container body thereof but also alid to be fitted to the container body is manufactured. Similarly to thecase of the container body, the opening peripheral edge of the lid iscut out of a synthetic resin sheet. Therefore, by forming the openingperipheral edge of the lid in a corrugated shape, the opening peripheraledge of the lid can have a soft touch instead of a sharp touch.

FIG. 5 is an illustrative plan view of a container body 1 or a lid 18,in which a flange 11 is shown by cross-hatching. Any of the corrugatedshapes as above-mentioned can be applied to the peripheral edge 11 a ofthis flange 11. Further, when the flange 11 is provided with a lug orprojection 15 for picking at the time of fitting the lid to thecontainer body or opening the fitted lid, the outer peripheral edge ofthis lug 15 is preferably corrugated.

As shown in FIG. 6, when the container body 1 and the lid 18 areconnected to each other for folding at a contact portion 16, corrugatedshapes can be applied to the outer peripheral edge of the flange 11 ofthe container body and the outer peripheral edge of the lid 18 exceptthe outer peripheral edge of the contact portion 16.

Further, when the projection 15 is projected, the outer peripheral edgeof the projection 15 is preferably corrugated.

In the above-mentioned description with reference to FIGS. 5 and 6,substantially the whole of the outer peripheral edge of the flange 11 ofthe container body 1 or the lid 18 has a corrugated shape. However, notthe whole but optional portions of the outer peripheral edge may have acorrugated shape.

In the above-mentioned embodiments, provided is an outwardly extendedflange at the opening of the container body or the lid. However, ifthere is no flange at the periphery of the opening of the container bodyor the lid, the opening peripheral edge can be corrugated.

FIGS. 7(A)-(C) are illustrative vertically sectional views of threekinds of container bodies. In the case that a flange 11 is provided atthe periphery of the opening as shown in FIG. 7(A), the outer peripheraledge (T1 in FIG. 7(A)) of the flange 11 can be formed in a corrugatedshape. In the case of a container body having a shape as shown in FIG.7(B), the outer peripheral edge T2 can be formed in a corrugated shape.And in the case of a container body having a shape as shown in FIG.7(C), the outer peripheral edge T3 can be formed in a corrugated shape.

FIGS. 8(A) and 8(B) are illustrative vertically sectional views ofexamples of the shape of a lid. In the case of FIG. 8(A), the outerperipheral edge T4 of the flange of the lid can be formed in acorrugated shape. And in the case of FIG. 8(B), the downward openingperipheral edge T5 encompassing the opening can be formed in acorrugated shape.

Now, a method for manufacturing a container body of FIG. 3 will bedescribed with reference to FIGS. 9 and 10 in the following.

A synthetic resin sheet from a whole roll is fed on a metal mold P1 formolding. The sheet is deformed in line with the shape of the metal moldP1, then transferred to a trimming die and cut by a cutting machinehaving e.g. a Thomson blade, whereby a molded container is separatedfrom the sheet.

One example of a metal mold P1 for molding is shown in FIG. 9. In themetal mold P1 for molding, at least the part for molding a flange 11 isformed in a corrugated shape W finely corrugated in the verticaldirection. By molding a sheet using this metal mold P1, the flange 11 ofthe container body 1 can be formed in a vertically corrugated shape.

FIG. 10 shows an example of cutting operation of a container body moldedof a sheet by a trimming die P2. In this example, a Thomson blade C isused. The edge of the Thomson blade C is formed in a corrugated shapecorrugated in the direction vertical to the paper surface of thedrawing. By using such a Thomson blade C, the peripheral edge of theflange can be corrugated in waveforms not only in the vertical directionbut also in the horizontal direction.

If a flange has been corrugated in the vertical direction as shown inthe embodiments of FIGS. 3 and 4, the outer peripheral edge of theflange cut by a cutting blade such as a Thomson blade having a straightblade edge is vertically waved in a side view (in the horizontaldirection), though it is straight in a plan view. Therefore, bypreliminarily corrugating a flange in the vertical direction, a cuttingblade having a straight blade edge can be used, so that a packagingcontainer can be easily manufactured.

It is preferable that an opening peripheral edge of a packagingcontainer is cut in an atmosphere temperature range of 15° C.-55° C.This is because if the temperature of a molded product is not higherthan 15° C., the molded product is apt to be cracked to become a badproduct, and on the contrary, the temperature of a molded product is notlower than 55° C., the molded product is apt to be softened anddeformed.

Although embodiments of the present invention have been described andillustrated in detail, it is clearly understood that these are by way ofillustration and example only and are not to be taken by way oflimitation, and the spirit and scope of the present invention arelimited only by the terms of the appended claims.

This application corresponds to the Japanese Patent Application No.2002-226431 filed in the Japan Patent Office on Aug. 2, 2002 and theJapanese Patent Application No. 2003-103250 filed in the Japan PatentOffice on Apr. 7, 2003, and the whole disclosures of these Japaneseapplications are incorporated in this application by citation.

1. A packaging container molded of a synthetic resin sheet in apredetermined shape, a peripheral edge encompassing an opening of thepackaging container being corrugated.
 2. A packaging container accordingto claim 1, in which the difference between the top and the bottom ofthe waveform of the corrugation is in the range of 0.2-1.0 mm and thepitch (the distance between the tops or the bottoms of the waveforms) ofthe corrugation is in the range of 0.5-5.0 mm.
 3. A packaging containeraccording to claim 2, in which the difference between the top and thebottom of the waveform of the corrugation is not more than 0.5 mm andthe pitch (the distance between the tops or the bottoms of thewaveforms) of the corrugation is not more than 1.0 mm.
 4. A packagingcontainer according to claim 1, in which an outer peripheral edge of thepackaging container is corrugated by providing minute projections andminute recesses throughout a flange formed at the periphery of theopening of the packaging container and then cutting the outer peripheryof the flange provided with the minute projections and the minuterecesses.
 5. A method for manufacturing a packaging container includinga step of molding a synthetic resin sheet into a predetermined shapeusing a metal mold for vertically corrugating a part outwardly projectedfrom an opening of the packaging container, and a step of transferringthe sheet-molded product obtained in the above-mentioned step to atrimming die and cutting the peripheral edge encompassing the openingusing a cutting blade having a blade edge which is straight orcorrugated in the direction of the length of the blade.
 6. A method formanufacturing a packaging container according to claim 5, in which thestep of cutting using the cutting blade is carried out in an atmospheretemperature range of 15° C.-55° C.
 7. A packaging container according toclaim 2, in which an outer peripheral edge of the packaging container iscorrugated by providing minute projections and minute recessesthroughout a flange formed at the periphery of the opening of thepackaging container and then cutting the outer periphery of the flangeprovided with the minute projections and the minute recesses.
 8. Apackaging container according to claim 3, in which an outer peripheraledge of the packaging container is corrugated by providing minuteprojections and minute recesses throughout a flange formed at theperiphery of the opening of the packaging container and then cutting theouter periphery of the flange provided with the minute projections andthe minute recesses.